Interleaved transformer winding having three parallel connected conductors

ABSTRACT

A disc-type interleaved winding for transformers. Current is conducted through the winding by three conductors connected in parallel and interconnected between the coil discs to provide three different conduction paths. The first and third conduction paths are transposed between adjacent coil discs and progress in radially opposite directions through adjacent coil discs. The second conduction path forms a looping pattern throughout the winding with the conductor forming the second conduction path physically positioned between the other two conductors in each coil disc.

United States Patent 1191 Yannucci et al.

INTERLEAVED TRANSFORMER WINDING HAVING THREE PARALLEL CONNECTEDCONDUCTORS [75] Inventors: Dean A. Yannucci, Warren,

Ohio; Robert I. Van Nice,

Sharon, Pa.

Pittsburgh, Pa.

'Assigneez Westinghouse Electric Corporation,

Filed: Nov. 10, 1972 [21] Appl. No.: 305,387

US. Cl. 336/70, 336/187 Int. Cl. 1101f 27/28 Field of Search 336/186,187, 69,

[56] References Cited UNITED STATES PATENTS 10/1967 Baker et al. 336/1877 9/1969 Dutton 336/187 1 Oct. 16, 1973 FOREIGN PATENTS OR APPLICATIONS786,126 11/1957 Great Britain.... 336/187 271968 Nether1ands.... 336/187Primary Examiner--Thomas J. Kozma Attorney-A. T. Stratton et al.

[57] ABSTRACT A disc-type interleaved winding for transformers. Currentis conducted through the winding by three conductors connected inparallel and interconnected between the coil discs to provide threedifferent conduction paths. The first and third conduction paths aretransposed between adjacent coil discs and progress in radially oppositedirections through adjacent coil discs. The second conduction path formsa looping pattern throughout the winding with the conductor forming thesecond conduction path physically positioned between the other twoconductors in each coil disc.

9 Claims, 2 Drawing Figures BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates, in general, to electrical inductiveapparatus and, more specifically, to interleaved transformer windingshaving three conductors.

2. Description of the Prior Art When a transformer winding isconstructed to carry a relatively large amount of current, multipleconductors connected in parallel are frequently used. By using multipleconductors instead of one large conductor, the eddy current losses inthe winding are reduced, and connections and transpositions within thewinding are less difficult to make due to the better flexibility of themultiple conductor lead.

The use of interleaved windings to increase the series capacitance of awinding structure is well known. Due to the increased series capacitanceprovided by interleaving, the impulse voltage characteristics of thewinding structure are improved. It is also known that the seriescapacitance of transformer windings is related to the voltage differencebetween adjacent conductors, with a larger voltage difference providingmore energy storage and a higher series capacitance. v

Arrangements for interleaving conductors to increase the seriescapacitance of a transformer winding having three conductors connectedin parallel are known by those skilled in the art. Although the priorart arrangements are beneficial electrically, the construction thereofis complicated and costly due to the physical arrangement of theinterleaving connections and to the insulation required around theconductors.

It is desirable, and it is an object of this invention, to provide athree-conductor interleaved transformer winding which may be constructedeasily and inexpensively.

SUMMARY OF THE INVENTION There is disclosed herein a new and usefulthreeconductor interleaved transformer winding. The winding includes atleast four coil discs which are axially located at different positionsin the winding. The three conductors are wound and interconnected toprovide first, second and third conduction paths through the discs ofthe winding. The first and third conduction paths progress in a firstradial direction through one coil disc and then in a second radialdirection, which is opposite to the first radial direction, through anadja cent coil disc. The same pattern is repeated in the other discs ofthe winding. Thus, the first and third conduction paths progress inopposite directions in adjacent coil discs throughout the winding.

The coil discs are arranged into first, second, third and fourth axialpositions throughout the winding. The second conduction path forms alooping path throughout the winding. The second conduction pathprogresses in the second radial direction through the coil disc in thesecond position, then in the first radial direction through the coildisc in the first position, then in the second radial direction throughthe coil disc in the fourth position, and then in the first radialdirection through the coil disc in the third position. This pattern isrepeated throughout every four discs of the winding.

With the arrangement disclosed herein, conductor insulation having arelatively high voltage breakdown strength is only required on one ofthe three conductors. The interleaving of the conductors provides awinding having a high series capacitance. In addition, theinterconnections between coil discs are relatively easy to construct.

BRIEF DESCRIPTION OF THE DRAWING Further advantages and uses of thisinvention will become more apparent when considered in view of thefollowing detailed description and drawing, in which:

FIG. 1 is a partial, sectional view of a transformer having athree-conductor interleaved winding; and

FIG. 2 is a schematic diagram of the interleaved winding shown in FIG.1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout the followingdescription, similar reference characters refer to similar members orelements in all the figures of the drawing.

Referring now to the drawings, and FIG. 1 in particular, there is showna partial, sectional view of a power transformer having an interleavedwinding 10. The winding 10 is illustrated as a high-voltage windingwhich is positioned around the low-voltage winding 12. Insulation 14insulates the low-voltage winding 12 from the magnetic core 16 and fromthe interleaved highvoltage winding 10.

The winding 10 includes a plurality of pancake winding sections or coildiscs, such as coil discs 18, 20, 22 and 24. The coil discs 18 20, 22and 24 are positioned at different axial positions throughout thewinding 10 as is illustrated in FIG. 1. It is within the contemplationof this invention that more than four coil discs may comprise thewinding 10. The terminals 26, 28 and 30 may be connected together and toassociated electrical apparatus, such as a high-voltage bushing.Similarly, the terminals 32, 34 and 36 may be connected together and toa bushing or they may be connected to additional coil discs withoutbeing connected together when the winding 10 comprises more than fourcoil discs.

Each coil disc is wound with three conductors which are denoted asconductors A, B and C. The conductors are spirally wound and areradially disposed on each other throughout the winding 10. In coil disc18, the conductor A at conductor position A0 is wound around thelow-voltage winding 12, the conductor B is wound around the conductor A,and the conductor C is wound around the conductor B. Although notcompletely illustrated, insulation material covers each conductor. Also,each conductor may comprise more than one wire strand.

Although the conductor positions A0, A1, A2, etc. designate differentphysical positions of the electrical conductor A, convenience andcommonly accepted practice will be adhered to in this description byreferring to such positions as conductors. Each group of threeconductors completes a conductor-turn. For example, conductors A0, B3and C0 form the start or first conductor-turn 38 of coil disc 18, andconductors A9, B12 and C9 form the finish or second conductor turn 40 ofthe coil disc 22. Any number of conductor-turns may be wound between thefirst and second conductorturns; however, only two intermediateconductor-turns are illustrated in each coil disc of FIG. 1 for clarity.The winding may be constructed in reverse relationship without departingfrom the spirit of the invention. In reverse relationship, the firstconductor-tums, such as the first conductor-turn 38, would be positionedon the outside of the winding as finsih conductor-turns, such as thesecond conductor-turn 40.

The numbers following the conductor designators A,

B and C indicate the relative voltage existing on the particularconductor at that location. For example, the voltage existing onconductor A4 in coil disc 20 is two times the voltage existing onconductor A2 in coil disc 18 since the conductor A has progressed twoturns in going from conductor A2 to conductor A4. The conductors aroundwhich the other conductors in the same conductor-turn are wound, such asconductors A0 and C6, will be referred to as the first conductor in theconductor-turns. The conductors which are wound around the otherconductors in the same conductor-turn, such as conductors C0 and A6,will be referred to as the third conductor in the conductor-turns. Theconductors which are located between the other two conductors of thesame conductor-turn, such as conductors B3 and B9, will be referred toas the second conductor in the conductor-turns. Although referred to asconductors, it'is emphasized again that they denote a position in aconductor-turn and may or may not be the same physical conductor at asimilar position in another conductor-turn.

As can be seen in FIG. 1, the first conductor-turn 38 of the first coildisc 18 has its first and third conductors, A and C respectively,connected to the terminals 26 and 28. The terminal 30 is connected tothe second conductor B of the second conductor-turn of the second coildisc 20. Conductors A and C are spirally wound around the low-voltagewinding 12 and progress outwardly to the second conductor-turn of thecoil disc 18. Conductor B spirals inwardly to the first conductorturn ofthe coil disc 20 and is interconnected to the second conductor B of thefirst conductor-turn 38 of the first coil disc 18 by the interconnectinglead 44.

The conduction paths between the terminals 26 and 32 and between theterminals 28 and 34 progress from the first conductor-turn to the secondconductor-turn of coil disc 18, from the second conductor-turn to thefirst conductor-turn of coil disc 20, from the first conductor-turn tothe second conductor-turn of the coil disc 22, and from the secondconductor-turn to the first conductor-turn of coil disc 24. Thetransposed interconnecting leads 46, 48 and 50 connect the appropriateconductors together between adjacent conductorturns. Transposing theleads 46, 48 and 50 reduces losses caused by circulating currents in theconductors A and C.

The conduction path between the terminals 30 and 36 progresses from thesecond conductor-turn to the first conductor-turn of the coil disc 20,from the first conductor-turn to the second conductor-turn of the coildisc 18, from the second conductor-turn to the first conductor-turn ofthe coil disc 24, and from the first conductor-turn to the secondconductor-turn of the coil disc 22. lnterconnecting leads 44, 52 and 54provide the necessary electrical connection between the appropriateconductor-turns.

With the arrangement shown in FIG. 1, the voltage between the conductorsA and C is substantially equal to zero in the same conductor-turn. Thus,where the conductors A and C are physically adjacent to each other, suchas in the transposed leads 46, 48 and 50, the insulation materialdisposed on the conductors A and C need not have a relatively highvoltage breakdown strength. Since the voltage between the conductors ofradially adjacent conductor-turns is equal to the voltage of one turn,the insulation on these conductors, such as CO and Al, must only besufficient to insulate the voltage equal to the voltage induced in oneturn of the conductor.

Prior art three-conductor arrangements require a substantial amount ofconductor insulation because they have a considerable amount of voltagebetween each conductor of a conductor-turn. In the present invention,the greatest amount of voltage difference exists between conductor B andthe other conductors. Thus, relatively high strength insulation needonly be applied to the conductor B. Therefore, a space and materialsavings may be realized by utilizing the present invention over theprior art. The additional insulation around the conductor B is indicatedby the thicker insulation 58 which extends around conductor B. It iswithin the contemplation of this invention that the insulation 58 neednot be thicker if it consists of a material having a higher breakdownstrength than the insulation around conductors A and C.

The degree of interleaving of the conductors used in this invention isknown as twin interleaving, that is, where the maximum voltagedifference between conductors equals the voltage developed in all theturns of one coil disc. One looping conductor path is required. Theother two conductor paths are continuous throughout the winding 10.Within the winding 10, no interconnections are required which connect afirst conductor-turn to a second conductor-turn. Thus, relatively longinterconnections are not required;

FIG. 2 is an electrical schematic diagram representing the winding 10.Corresponding to FIG. 1, the direction indicated by the arrow 60represents the direction going from the inside of the winding 10 to theoutside of the winding 10. Since as previously stated, the winding 10may be constructed in reverse relationship, the direction indicated bythe arrow 60 will be referred to as the first direction to eliminatereference to the physical construction of the winding 10. Similarly,arrow 62 represents a second direction which is opposite to that of thefirst direction.

From FIG. 2, it can be seen that a first conduction path begins atterminal 26 and progresses in the first direction through coil disc 18,in the second direction through coil disc 20, in the firstdirectionthrough coil disc 22, and in the second direction through coildisc 24. A third conduction path between the terminals 28 and 34progresses in a similar manner. A second conduction path between theterminals 30 and 36 pro-' gresses in the second direction through coildisc 20, in the first direction through coil disc 18, in the seconddirection through coil disc 24, and in the first direction through coildisc 22. The vertical position of the conductor coils, such as coils 64,66 and 68 represents the relative radial position of the conductor inthe physical accompanying drawing, shall be interpreted as illustrativerather than limiting.

We claim as our invention:

1. A winding for electrical inductive apparatus, comprising:

at least, first, second, third and fourth coil discs, said second coildisc being axially positioned between said first and third coil discs,said third coil disc being axially positioned between said second andfourth coil discs;

first, second and third electrical conductors forming first, second andthird conduction paths through said coil discs;

said first and third conduction paths progressing in a first directionthrough said first coil disc, in a second direction through said secondcoil disc, in the first direction through said third coil disc, and inthe second direction through said fourth coil disc, said first andsecond directions being opposite each other; and

said second conduction path beginning in second coil disc andprogressing in the second direction through said second coil disc, inthe first direction through said first coil disc, in the seconddirection through said fourth coil disc, and in the first directionthrough said third coil disc, respectively.

2. The winding of claim 1, wherein the second conductor is positionedbetween the first and third conductors throughout each of said coildiscs.

3. The winding of claim 1, wherein the first and third conductors aretransposed between each coil disc.

4. The winding of claim 1, wherein the second conductor is covered withan insulation structure having a higher voltage breakdown strength thanthat of insulation covering the first and third conductors.

5. A winding for electrical inductive apparatus, comprising:

at least, first, second, third and fourth coil discs having first andsecond conductor-turns, said second coil disc being axially positionedbetween said first and third coil discs, said third coil disc beingaxially positioned between said second and fourth coil discs;

first, second and third electrical conductors forming first, second andthird conduction paths through said coil discs;

said first and third conduction paths beginning at the firstconductor-turn of said first coil disc and progressing to the secondconductor-turn of said first coil disc, to the second conductor-turn ofsaid second coil disc, to the first conductor-turn of said second coildisc, to the first conductor-turn of said third coil disc, to the secondconductor-turn of said third coil disc, to the second conductor-turn ofsaid fourth coil disc, and to the first conductor-turn of said fourthcoil disc; and

said second conduction path beginning at the second conductor-turn ofsaid second coil disc and progressing to the first conductor-turn ofsaid second coil disc, to the first conductor-turn of said first coildisc, to the second conductor-turn of said first coil disc, to thesecond conductor-turn of said fourth coil disc, to the firstconductor-turn of said fourth coil disc, to the first conductor-turn ofsaid third coil disc, and to the second conductor-turn of said thirdcoil disc.

6. The winding of claim 5, wherein the second conductor is radiallypositioned between the first and third conductors in everyconductor-turn.

7. The winding of claim 5, wherein the first and third conductors aretransposed between each coil disc.

8. The winding of claim 5, wherein the second conductor is covered withan insulation structure having a higher voltage breakdown strength thanthat of insulation covering the first and third conductors.

9. A winding for electrical inductive apparatus, comprising;

at least, first, second, third and fourth coil discs, said second discbeing axially positioned between said first and third coil discs, saidthird coil disc being axially positioned between said second and fourthcoil discs;

first, second and third conductors each comprising at least oneelectrical strand, said second conductor being radially disposed oversaid first conductor and said third conductor being radially disposedover said second conductor, said first, second and third conductorsbeing collectively and spirally disposed through each of said coil discsto form at least first and second conductor-turns, the firstconductor-turn of each coil disc being located at substantially the sameradial position in said winding, said conductors being electricallyconnected between conductor-turns to provide first, second and thirdconduction paths;

said first conduction path beginning at the first conductor of the firstconductor-turn of said first coil disc and progressing to the firstconductor of the second conductor-turn of said first coil disc, to thethird conductor of the second conductor-turn of said second coil disc,to the third conductor of the first conductor-turn of said second coildisc, to the first conductor of the first conductor-turn of said thirdcoil disc, to the first conductor of the second conductor-turn of saidthird coil disc, to the third conductor of the second conductor-turn ofsaid fourth coil disc, and to the third conductor of the firstconductor-turn of said fourth coil disc;

said second conduction path beginning at the second conductor of thesecond conductor-turn of said second coil disc and progressing to thesecond conductor of the first conductor-turn of said second coil disc,to the second conductor of the first conductor-turn of said first coildisc, to the second conductor of the second conductor-turn of said firstcoil disc, to the second conductor of the second conductor-turn of saidfourth coil disc, to the second conductor of the first conductor-turn ofsaid fourth coil disc, to the second conductor of the firstconductor-turn of said third coil disc, and to the second conductor ofthe second conductorturn of said third coil disc; and

said third conduction path beginning at the third conductor of the firstconductor-turn of said first coil disc and progressing to the thirdconductor of the second conductor-turn of said first coil disc, to thefirst conductor of the second conductor-turn of said second coil disc,to the first conductor of the first conductor-turn of said second coildisc, to the third conductor of the first conductor-turn of said thirdcoil disc, to the third conductor of the second conductor-turn of saidthird coil disc, to the first conductor of the second conductor-turn ofsaid fourth coil disc, and to the first conductor of the firstconductor-turn of said fourth coil disc.

1. A winding for electrical inductive apparatus, comprising: at least,first, second, third and fourth coil discs, said second coil disc beingaxially positioned between said first and third coil discs, said thirdcoil disc being axially positioned between said second and fourth coildiscs; first, second and third electrical conductors forming first,second and third conduction paths through said coil discs; said firstand third conduction paths progressing in a first direction through saidfirst coil disc, in a second direction through said second coil disc, inthe first direction through said third coil disc, and in the seconddirection through said fourth coil disc, said first and seconddirections being opposite each other; and said second conduction pathbeginning in second coil disc and progressing in the second directionthrough said second coil disc, in the first direction through said firstcoil disc, in the second direction through said fourth coil disc, and inthe first direction through said third coil disc, respectively.
 2. Thewinding of claim 1, wherein the second conductor is positioned betweenthe first and third conductors throughout each of said coil discs. 3.The winding of claim 1, wherein the first and third conductors aretransposed between each coIl disc.
 4. The winding of claim 1, whereinthe second conductor is covered with an insulation structure having ahigher voltage breakdown strength than that of insulation covering thefirst and third conductors.
 5. A winding for electrical inductiveapparatus, comprising: at least, first, second, third and fourth coildiscs having first and second conductor-turns, said second coil discbeing axially positioned between said first and third coil discs, saidthird coil disc being axially positioned between said second and fourthcoil discs; first, second and third electrical conductors forming first,second and third conduction paths through said coil discs; said firstand third conduction paths beginning at the first conductor-turn of saidfirst coil disc and progressing to the second conductor-turn of saidfirst coil disc, to the second conductor-turn of said second coil disc,to the first conductor-turn of said second coil disc, to the firstconductor-turn of said third coil disc, to the second conductor-turn ofsaid third coil disc, to the second conductor-turn of said fourth coildisc, and to the first conductor-turn of said fourth coil disc; and saidsecond conduction path beginning at the second conductor-turn of saidsecond coil disc and progressing to the first conductor-turn of saidsecond coil disc, to the first conductor-turn of said first coil disc,to the second conductor-turn of said first coil disc, to the secondconductor-turn of said fourth coil disc, to the first conductor-turn ofsaid fourth coil disc, to the first conductor-turn of said third coildisc, and to the second conductor-turn of said third coil disc.
 6. Thewinding of claim 5, wherein the second conductor is radially positionedbetween the first and third conductors in every conductor-turn.
 7. Thewinding of claim 5, wherein the first and third conductors aretransposed between each coil disc.
 8. The winding of claim 5, whereinthe second conductor is covered with an insulation structure having ahigher voltage breakdown strength than that of insulation covering thefirst and third conductors.
 9. A winding for electrical inductiveapparatus, comprising; at least, first, second, third and fourth coildiscs, said second disc being axially positioned between said first andthird coil discs, said third coil disc being axially positioned betweensaid second and fourth coil discs; first, second and third conductorseach comprising at least one electrical strand, said second conductorbeing radially disposed over said first conductor and said thirdconductor being radially disposed over said second conductor, saidfirst, second and third conductors being collectively and spirallydisposed through each of said coil discs to form at least first andsecond conductor-turns, the first conductor-turn of each coil disc beinglocated at substantially the same radial position in said winding, saidconductors being electrically connected between conductor-turns toprovide first, second and third conduction paths; said first conductionpath beginning at the first conductor of the first conductor-turn ofsaid first coil disc and progressing to the first conductor of thesecond conductor-turn of said first coil disc, to the third conductor ofthe second conductor-turn of said second coil disc, to the thirdconductor of the first conductor-turn of said second coil disc, to thefirst conductor of the first conductor-turn of said third coil disc, tothe first conductor of the second conductor-turn of said third coildisc, to the third conductor of the second conductor-turn of said fourthcoil disc, and to the third conductor of the first conductor-turn ofsaid fourth coil disc; said second conduction path beginning at thesecond conductor of the second conductor-turn of said second coil discand progressing to the second conductor of the first conductor-turn ofsaid second coil disc, to the second conductor of the firstconductor-turn of said first coil disc, to the second conductor of thesecond conductor-turn of said first coil disc, to the second conductorof the second conductor-turn of said fourth coil disc, to the secondconductor of the first conductor-turn of said fourth coil disc, to thesecond conductor of the first conductor-turn of said third coil disc,and to the second conductor of the second conductor-turn of said thirdcoil disc; and said third conduction path beginning at the thirdconductor of the first conductor-turn of said first coil disc andprogressing to the third conductor of the second conductor-turn of saidfirst coil disc, to the first conductor of the second conductor-turn ofsaid second coil disc, to the first conductor of the firstconductor-turn of said second coil disc, to the third conductor of thefirst conductor-turn of said third coil disc, to the third conductor ofthe second conductor-turn of said third coil disc, to the firstconductor of the second conductor-turn of said fourth coil disc, and tothe first conductor of the first conductor-turn of said fourth coildisc.